1. Field of the Invention
The present invention relates to the field of dental instruments, and more particularly to a novel dental impression tray for obtaining an impression of a patient's dentition, including an impression of both the upper and lower arches and registering their relationship to each other in a single procedure.
2. Brief Description of the Prior Art
Prior or conventional impression trays are incapable of taking accurate impressions in a consistent manner. In general, dental trays for obtaining an impression of a patient's dentition include a tray portion contoured to fit within the patient's mouth so that when the patient closes or bites his teeth, an impression is made in the impression material. Initially, the tray is loaded with a suitable setting impression material on both hemispheres of the tray and situated opposite to the desired dentition part whereupon the patient bites into the impression material to form an impression of the dentition in the material. After the impression material sets, it is used as a mold into which plaster or the like can be poured which, upon setting, forms a model of the dentition.
Prior attempts have been made to solve a variety of problems in the use of dental impression trays and one such attempt is disclosed in U.S. Pat. No. 4,689,010. However, problems and difficulties have been encountered which stem largely from the fact that it is difficult to retain the impression material in place during and particularly after the impression bite has been made. At times, the supporting layer for the impression material may be perforated by the sharp teeth of the patient during the taking of the impression. Also, conventional trays do not properly flex during the impression procedure. At the end of the procedure, the tray sometimes reverts to a previous configuration causing distortion of the impression.
Most conventional triple bite trays have experienced problems in the area of distortion. The process of taking the impression allows the impression material which is set within the tray on both sides of the gauze support at which time the patient bites into the unset impression material such as polyvinyl-siloxane and when the material is set or hardened, the impression tray along with the impression material will be removed from the mouth. It is at this point that the distortion occurs due to the memory found in the plastics or metals used in the construction of the tray. This memory found in the arches connecting the parallel walls is stronger than the memory found in the impression material. As the patient bites down into the impression, the tray flexes in a Buccal/Lingual direction, due to the strength of the muscle of mouth and the design of the walls. Upon removal of the impression and the tray, the memory that is present within the plastics and metals will flex back to the original position it was in prior to the impression being taken. The result is a distorted impression due to the fact that the memory of the impression material especially over the occlusal surfaces, which have exposed the gauze supports, is weaker than the memory of a plastic or metal retro molar arch. Wire allows flexing of the tray so that the memory of the impression material is stronger than that of the wire.